Question

In C#,

Is there a way to turn an automatic property into a lazy loaded automatic property with a specified default value?

Essentially, I am trying to turn this…

private string _SomeVariable

public string SomeVariable
{
     get
     {
          if(_SomeVariable == null)
          {
             _SomeVariable = SomeClass.IOnlyWantToCallYouOnce();
          }

          return _SomeVariable;
     }
}

into something different, where I can specify the default and it handles the rest automatically…

[SetUsing(SomeClass.IOnlyWantToCallYouOnce())]
public string SomeVariable {get; private set;}

Answer 1

No there is not. Auto-implemented properties only function to implement the most basic of properties: backing field with getter and setter. It doesn’t support this type of customization.

However you can use the 4.0 Lazy<T> type to create this pattern

private Lazy<string> _someVariable =new Lazy<string>(SomeClass.IOnlyWantToCallYouOnce);
public string SomeVariable => _someVariable.Value;

This code will lazily calculate the value of _someVariable the first time the Value expression is called. It will only be calculated once and will cache the value for future uses of the Value property